Pivoted breech bolt lock for automatic firearms



B. MAILLARD Dec. 4, 195] PIVOTED BREECH BOLT LOCK FOR AUTOMATIC FIREARMS 2 Si-lEETS-Sl-XEET 1 Filed Dec. 2'7, 1946 I n ye r? 2 0 Be/Ward MaZZZar-cl AZ'Zj/s Dec. 4, 1951 MAILLARD 2,577,026

PIVOTED BREECH BOLT LOCK FOR AUTOMATIC FIREARMS Filed Dec. 27, 1946 2 SHEETS SHEET 2 Fig. 6

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Patented Dec. 4, 1951 PIVOTED BREECH 1301.1v LOOK FOR AUTOMATIC FIREARMS Bernard Maillard, Geneva," Switzerland, assignor to Brevets Aero-Mecaniques S. A., a corporation of Switzerland Application December 27, 1946, Serial No. 718,661 In Switzerland January 16, 1946 2 Claims. (Cl. 89190) The present invention has for its subject an automatic firearm provided with a breech block Sliding in a breech case and with at least one bolt adapted to lock these two members relatively to one another.

In firearms of this type, the bolt generally has the shape of a lever hinged to one of these two members, that is to say to the breech block or to the breech case, so as to be capable of moving relatively to its support between a looking or active position and a neutral or retracted position. The movement of the bolt in the locking direction may then be controlled by the coming into engagement, at the moment of locking the breech block, of two ramps moving one relatively to the other and of which one is secured to the bolt. In the constructions proposed hitherto, the bolt is guided entirely in its support during its movement relatively to this support. It is, for example, hinged at one of its ends to the breech block, whilst its other end is guided by said breech block by means of surfaces which are cylindrical and concentric to the hinge axis. This arrangement is disadvantageous because the presence of small impurities between these surfaces results in braking the movements of the bolt relatively to its support. The bolt is liable to be wedged between the guide surfaces and to be subjected to considerable friction and rebounding which are detrimental to velocity of firing and produce rapid wear.

The object of the present invention is to eliminate these disadvantages. For this purpose, according to my invention, the bolt intended to lock the breech block with respect to the breech case is formed by a lever of which one of the ends engages in a housing provided in one of these two parts, the housing being so provided as to allow the bolt to oscillate between a locking or active position and a neutral or retracted posi-. tion, the other end of the lever having surfaces adapted to come into contact, in the retracted position, with cooperating surfaces of said housing, these surfaces of the bolt and of the housing being so shaped as to move away from one another when the bolt is moving away from its retracted position so as to leave said bolt loose in said housing for at least the end portion of its movement toward active or looking position.

An embodiment of my invention is shown by way of example in the accompanying drawings, wherein:

Fig. l is a view in elevation, partly in section of an automatic firearm.

Fig. 2 is a view in horizontal section on the line IIII of Fig. 3.

Figs. 3 and 4 are views in cross-section on the lines IIIIII and..IV:-IY of Fig; l.

Fig. 5 is a plan view of the bolt and rails on the breech case with which it co-operates.

Figs. 6, 7 and 8 are views in elevation, to a larger scale, of a portion of the firearm, in its different phases of operation. Theautomatic firearm shown in the drawings is provided, at the rear of a barrel II], with a. breech case Ii, in which can slide a breech formed by the following three elements: a breech block 12, a bolt [3 adapted to lock the breech block relatively to the breech case when a shot is being fired and safety means for securing bolt IS in its locking position. Said safety means is formed by two slides Id connected together by a peg l 5 and capable of sliding longitudinally relatively to breech block l2. The peg l5 passes through an elongated opening [6 provided in the breech block and carries a striker ll sliding in an axial hole I 8 which at the same time serves as, a seating for a return spring [9. The move- 'ment of slides I 4 relatively to breech block I2 is limited by the length of slot [6. Percussion springs 2!], bearing against projections 2| of the breech block, and against slides M, tend to move the latter forwardly relatively to the breech block. Bolt I3 is located in a housing22 provided in the lower part of the breech block (see Figs. 5 to 7). At its front end bolt I3 is provided with a cylindrical surface 23 forming a journal which cooperates with an open bearing 24, of the same shape, provided in the front wall of housing 22. At its upper portion the bolt is provided with a projection 25 adapted to engage a notch 26 cut in the bottom part of slides 14. It is limited at its rear end by three separate faces 21, 28, 29. Face 21 is adapted to come into contact, for the locking position, with a bearing surface 30 provided on a transverse member 3| rigid with the breech case N (Fig. 8).

When bolt 13 is in its retracted position (position shown in Fig. 1), it rests by its lower face 32 on the breech case. The face 28 of the bolt is located opposite a surface 33 provided on the breech block l2 and forming a portion of the rear wall of housing 22 (Fig. 6). Slides l4, urged by wall springs 19 and 20 and bearing against the face 29 of the bolt by a ramp 34, tend to push the latter forwardly against the hinge surface 24. The bolt is also provided with two lateral projections 35 (shown in Fig. 5). The front portion of these projections form ramps 36 located opposite ramps 31 provided on two Sta tionary rails 38 secured to the breech case. Ramps 36 and 31 are adapted to come into contact with one another slightly before the breech block in its closing movement, reaches the end of its stroke. The reaction to which the bolt is subjected by the ramp 3'! has a horizontal component which tends to cause face 28 to come into contact with surface 33 (Fig. 6). The bolt is thus subjected simultaneously to the reactions of ramps 31 and 34 and of surface 33, which 3 reactions: result in rapidly driving downwardly the rear part of the bolt, the front part of the bolt being journalled in bearings 24. The bolt then comes into engagement, by its face 21, with the notch 30 of the breech case. It is secured in its locking or active position (Fig; 8) by being covered by the rear portion of slides II which keep moving forward for the. purpose of producing percussion. It is to be observed that when the bolt leaves its retracted position (Fig. 6), to move toward its locking position, it loses contact with the inclined surface 33 and is. no longer guided longitudinally by the breech block housing. The bolt can thus oscillate freely, without being subjected to useless friction and without risk to Wedging. or rebounding. This tends to promote rapidity and uniformity in the movements of oscillation of the bolt, and to reduce wear of the various members.

In this form of construction the movement of oscillation of the bolt in the locking direction is produced by the combined action of ramps34 and 37,. but it is to be observed that the sole action of the ramp 34 may be sufficient to produce this movement.

The bolt remains secured in its locking positionduring the firing of the shot and until the burnt gases which are present in the bore of barrel [0, acting through the medium ofv a port 39, a cylinder 4!]. and pushers 4|, produce the recoil of slides I4. The inclination of the. rear face of. notch 39 is calculated to return the bolt automatically into. retracted position. when the projection 25. of said bolt can engage into the notch 26 of the slides which are now moving rearwardly so. that said bolt is. no. longer secured in its locking position.

The present invention may be applied in the case in which the bolt, instead of being hinged in the. breech block,.is hinged in the breech case. In this case the bolt, can co-operate, for. passing from its, retracted position to its locking. position, with ramps located on. the breech block. The breech case is then provided with a part adapted to come into contactwith a part of the bolt opposite the hinge point of thelatter, these parts being so inclined as to promote the, movement of the bolt in the locking direction.

I claim:

1. In an automatic firearm including. a barrel, the combination of a breech case havin a surface parallel to the axis of said barrel, a breech block slidable in said breech case in a direction parallel to said axis and having a surface in slidingengagement with saidsurface of the breech case,- one of said two last mentioned parts being providedwith an opening into the surface which is in said sliding engagement with the other of said two last mentioned parts, and a locking bolt having one end journalled in one end wall of said opening so as to be substantially pivotally movable with respect to the one of said two last mentioned parts between a retracted release position in which it-is' in alignment with the surface of the one of said two last mentioned parts and alocked position in which it projects therefrom, said engaging surface of the other of said two last mentioned partsbeing provided with a notch for engaging said locking bolt in the locked position thereof to prevent rearward movement of said breech block, a second end wall ofsaid opening. opposite said journalled end being generated by the end of a first radius vector having itsorigin substantially coinciding with the center of curvature of said journal and increasing in length over itsarc of movement from the bottom of the opening to the outer surface thereof; and when the locking bolt is in retracted position, the end of said locking bolt opposite the journalled end being in surface engagement with a substantial portion of said second end wall of said opening,

the engagement area of said end of said locking bolt opposite the journalled end and said second end wall of said opening being generated by the end of a second radius vector also having its origin substantially coinciding with the center of curvature of said journal and increasing in length over its arc of movement correspondingly to the increasing length of said first radius vector, whereby upon pivotal movement of the bolt from the retracted position to the locked position, the end of said bolt opposite said journalled end moves apart from said second end wall of said opening to form a continuously and progressively increasing gap.

2. In an automatic firearm: including a barrel, the combination ofv a breech case having a surface parallel to the axis of said barrel, a breech block slidable in said breech case in a direction parallel to said axis and. having a surface in sliding engagement with said surface of the breech case, said breech block being provided with an opening intothe surface which is in sliding engagement with said surface of the. breech case, and a locking bolt having one end journalled in one end wall of said openingv so as to be substantially pivotally movable with respect to said breech block between a retracted. release position for which it is in, alignment. with said breech block. surface and. a locked position for which it projects therefrom, said. breech case surface being provided. with. a. notch. for engaging said locking bolt inthe locked position thereof to prevent rearward movement of said breech block, a second end wall of said opening opposite said journall-ed. end. being generated by the end of a first radius vector having its origin substantially coinciding with. the center of curvature of said journal and increasing in length over its arc of movement from the bottom of the opening to the outer surface thereof; and when said locking bolt is in retracted position the end of said locking bolt opposite said j'ournall'ed end being in surface engagement with a substantial portion of said second end 'wall of said opening opposite said journalled' end as generated by the said first radius vector, the engagement area of said end of said locking bolt opposite said journalled end and said second, end wall of said opening being generated by the end of a second radius vector also having its origin substantially coinciding with the center of curvature of said journal and increasingv in length over its arc of movement and correspondingly to the increasing length of said first radius vector, whereby upon the pivotal movement of the bolt from the retracted position to. the locked position, said end of. said bolt opposite said journalled. end moves apart from said second: end wall of said opening to form a continuously and progressively increasing gap.

BERNARD MAILLARD.

Name Date Birkigt May 7, 1940 Number 

